Crossing things out in an immaculate PowerPoint slide with a rough, red paint brush can make a point strongly: "with our technology you can skip buying that new server"
I use a simple PowerPoint 2007 "glow" to get a graffiti-style effect. In the image below, I selected the "Boopee" font (standard in PowerPoint 2007) to which I applied a red glow and a gradient text fill (bright red, with a darker red). The background image was purchased on iStockPhoto. Let me know in the comments if you need more detailed instructions.
The French are just so good in inventing words: "taggeur" for graffiti artist (or vandal). Brilliant.
Be sure to avoid setting yourself up for disaster when using non-standard fonts in a PowerPoint presentation.